G protein-coupled receptors

Definition

G protein-coupled receptors (GPCRs) are a large family of membrane proteins that play a critical role in cellular communication by transmitting signals from the outside of a cell to its interior. They are activated by various ligands, including hormones and neurotransmitters, and initiate intracellular signaling cascades that affect numerous biological processes, such as vision, taste, and immune responses.

5 Must Know Facts For Your Next Test

1. GPCRs are one of the largest and most diverse groups of membrane proteins, with over 800 distinct types identified in humans.
2. They play crucial roles in various physiological processes, including sensory perception, mood regulation, immune system function, and development.
3. GPCRs work by activating G proteins, which are intracellular proteins that relay signals to other cellular effectors like enzymes or ion channels.
4. The binding of a ligand to a GPCR leads to conformational changes in the receptor, which trigger the exchange of GDP for GTP on the associated G protein, activating it.
5. Many pharmaceutical drugs target GPCRs due to their involvement in numerous disease processes, making them significant for drug discovery and development.

Review Questions

• How do G protein-coupled receptors initiate intracellular signaling upon ligand binding?
  • When a ligand binds to a G protein-coupled receptor, it causes a change in the receptor's shape. This conformational change allows the GPCR to interact with an associated G protein inside the cell. The G protein then exchanges GDP for GTP, becoming activated and proceeding to influence downstream signaling pathways through second messengers or other effector proteins.
• What is the significance of second messengers in the context of G protein-coupled receptors' function?
  • Second messengers play a vital role in amplifying and propagating signals initiated by G protein-coupled receptors. Once the GPCR is activated, it can stimulate various enzymes, such as adenylate cyclase or phospholipase C, leading to the production of second messengers like cAMP or IP3. These molecules then further propagate the signal within the cell, resulting in specific physiological responses and cellular actions.
• Evaluate the impact of G protein-coupled receptors on drug development and therapeutic interventions.
  • G protein-coupled receptors have a significant impact on drug development because they are involved in a wide array of physiological functions and disease processes. Many existing medications target GPCRs to modulate their activity and achieve desired therapeutic effects. This has led to ongoing research aimed at discovering new drugs that selectively interact with specific GPCRs, potentially leading to better treatments for conditions like depression, hypertension, and cancer.

Related terms

Ligand: A molecule that binds to a receptor to initiate a biological response, often influencing the activity of the receptor.

Second messengers: Intracellular signaling molecules released in response to the activation of a receptor, amplifying the signal and triggering specific cellular responses.

Signal transduction: The process by which a cell converts an external signal into a functional response, often involving a series of molecular events initiated by receptor activation.